High cycle fatigue and fatigue crack propagation behaviors of beta-annealed Ti-6Al-4V alloy

Abstract

Background: The effect of beta annealing on high cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of Ti64 alloy were examined, and the results were compared to those of mill-annealed counterpart. Methods: The tensile tests, stress-controlled HCF tests, and FCP tests were conducted, and the fractographic and micrographic analyses were performed before and after the tests. Results: The beta-annealed Ti64 specimen showed inferior HCF properties as compared to the mill-annealed counterpart, as a result of lower yield strength. On the other hand the resistance to FCP of beta-annealed Ti64 specimen was higher than that of mill-annealed counterpart in low and intermediate.K regime. Conclusions: Relatively easy fatigue crack initiation at the colony boundaries of beta-annealed Ti64 specimen reduce the resistance to HCF. The resistance to FCP of beta-annealed Ti64 specimen increased significantly particularly in low Delta K regime along with severe crack branching and deflection.